1. Field of the Invention
The present application is based on Japanese Patent Applications No. 2010-25353 filed on Feb. 8, 2010 and No. 2010-235269 filed on Oct. 20, 2010, the entire contents of which are incorporated herein by reference.
The invention relates to a soft dilute copper alloy material having high conductivity and a long bending life even though it is a soft material, a soft dilute copper alloy wire, soft dilute copper alloy sheet, a soft dilute copper alloy stranded wire, and a cable, a coaxial cable and a composite cable using the same.
2. Description of the Related Art
In recent science and technology, electricity is used for everything such as electric power as a power source or electric signals, etc., and conductors such as cables or lead wires are used for transmission thereof. Metals having high conductivity such as copper (Cu) or silver (Ag) are used as a material of such conductors, and particularly, copper wires are used very often in view of the cost.
Although it is generically called “copper”, it is broadly classified into hard copper and soft copper depending on a molecular arrangement thereof. In addition, various types of copper having desired properties are used depending on the intended use.
A hard copper wire is often used for a lead wire for electronic component. Meanwhile, a cable used in electronic devices, etc., such as medical equipment, industrial robot or notebook computer is used in an environment in which a combined external force of extreme bending, torsion and tension, etc., is repeatedly applied. Therefore, a rigid hard copper wire is unsuitable as such a cable and a soft copper wire is used instead.
A conductor used for such an application is required to have conflicting characteristics, which are good conductivity (high conductivity) and good bending characteristics. Accordingly, a copper material maintaining high conductivity and flexibility has been developed to date (see JP-A 2002-363668 and JP-A 9-256084).
For example, JP-A 2002-363668 relates to a flexible cable conductor having good tensile strength, elongation properties and conductivity, and particularly, a flexible cable conductor is described in which a wire rod is formed of a copper alloy made of oxygen-free copper (OFC) with a purity of not less than 99.99 wt % containing indium (In) with a purity of not less than 99.99 wt % at a concentration range of 0.05 to 0.70 mass % and phosphorus (P) with a purity of not less than 99.9 wt % at a concentration range of 0.0001 to 0.003 mass %.
Meanwhile, JP-A 9-256084 describes a flexible copper alloy wire containing 0.1 to 1.0 wt % of indium (In), 0.01 to 0.1 wt % of boron (B) and copper (Cu) as the remainder.
However, in JP-A 2002-363668 which discloses the invention only related to a hard copper wire, flexibility is not specifically evaluated. A soft copper wire having better flexibility is not examined at all. In addition, the invention described in JP-A 2002-363668 has a disadvantage in that conductivity is low due to the large amount of additional elements. Therefore, it cannot be considered that the soft copper wire is sufficiently examined in JP-A 2002-363668. Meanwhile, JP-A 9-256084 which discloses the invention related to a soft copper wire also has a disadvantage in that conductivity is low due to the large amount of additional elements in the same manner as the hard copper wire described in JP-A 2002-363668.
On the other hand, it is considered that high conductivity is ensured by selecting a highly conductive copper material such as oxygen-free copper (OFC), etc., as a raw copper material.
In addition, when oxygen-free copper (OFC) is used as raw material without adding any other elements in order to maintain high conductivity, a crystalline structure in the oxygen-free copper wire can be made finer by drawing a copper wire rod at an increased compression ratio so as to improve flexibility. The copper alloy material made by such a method is work-hardened due to the wire drawing process and is thus suitable for application as a hard wire rod. However, there is a problem that such a copper alloy material cannot be used for a soft wire rod.